Fragaria ananassa DAM4 expression correlates with vegetative growth during endodormancy breaking

Dormancy-Associated MADS-BOX (DAM)3 and DAM4 have been described as potential regulators of winter dormancy in cultivated strawberry (Fragaria x ananassa Duch.). These genes are upregulated under short day conditions and downregulated under chilling conditions. The aim of the current work is to test the hypothesis that the expression of DAM3 and DAM4 correlates negatively with vegetative growth during dormancy induction and breaking. The expression of DAM3 and DAM4 as well as plant morphology and physiology were analyzed during a period of endodormancy induction and breaking. Furthermore, to analyze whether there exists a correlation between DAM expression and chill requirement, DAM3 and DAM4 expression was compared between cultivars with different chill requirements. Lastly, the DAM1, DAM2, DAM3, and DAM4 expression of concurrently growing summer and winter leaves was compared at multiple stages of dormancy-breaking. DAM3 and DAM4 expression negatively correlated with leaf area and petiole length. We conclude that DAM3 and DAM4 expression patterns are consistent with that of regulators of endodormancy. DAM4 expression in particular correlates strongly with vegetative growth during endodormancy breaking. DAM3 or DAM4 expression were not found to correlate with the cultivar-specific chill requirements. We theorize that the chill requirement of strawberry cultivars is based on vegetative growth and does not affect DAM expression or endodormancy status. Lastly, no relevant differences in DAM expression were found between summer and winter leaves.